Though it's police unions that protect bad cops, Black Lives Matter activists and politician-supporters are oddly silent on the subject.

When Attorney General Loretta Lynch spoke to the Fraternal Order of Police last month, she came with a message: “thank you for being the peacemakers.” Black Lives Matter activists were taken aback by her characterization, with one prominent activist, DeRay McKesson, tweeting, “we have officially entered the twilight zone.”

If you have paid any attention to the ongoing debates about law enforcement and black bodies, this will not surprise you.

On July 17, 2014, Eric Garner was killed during an attempted arrest — Garner was selling loose cigarettes — when an officer placed him in a chokehold. The head of the Patrolmen’s Benevolent Association, Pat Lynch, told reporters that it was “not a chokehold,” and that the city’s Mayor, Bill De Blasio, needs to “support New York City police officers unequivocally.” A CBS News headline summarized the police union’s response as arguing that Garner was “complicit in (his) own death,” by refusing arrest and being overweight.

Ed Mullins, the head of the Sergeants Benevolent Association, called the $5.9 million settlement the city made with Garner’s family “shameful” and “obscene.” “Where is the justice for New York taxpayers?” he asked.

When two NYPD officers were killed by a madman who sought “revenge” in the wake of Garner’s death, Lynch used their deaths as political leverage, claiming that the “blood on the hands starts at City Hall in the office of the mayor.”

It’s not just New York. After police shot and killed 12-year-old Tamir Rice within seconds of arriving on scene, the Cleveland Police Department had to distance itself from its local police union leader. “This shooting was justified,” Jeffrey Follmer, the Cleveland Police Union President told reporters. “It’s a tragedy for this 12-year-old, but it was justified.”

In Baltimore, after Freddie Gray was found dead with a severed spine while detained by police, Baltimore police union officials both denied the police had any responsibility for Gray’s death, and then worked to undermine the credibility of Baltimore State’s Attorney, Marilyn Mosby, who was charged with investigating the case.

Time after time, it is police union leadership that defends and protects the cops involved in the cases that have fueled the Black Lives Matter movement. Time after time, police union leaders provide voice to the very arguments and justifications that Black Lives Matter activists, and the politicians that align with the movement, seek to combat.

Indeed, the Fraternal Order of Police has consistently sought to prevent the federal government from addressing issues of police conduct and law enforcement. After the White House announced restrictions on the military-grade equipment that could be used by local police forces, the Fraternal Order of Police accused the White House of politicizing officers’ safety, because they “don’t like the optics.”

Whatever you think of the comments from police union officials highlighted above, there is no doubt that they strike at the very heart of what Black Lives Matter is all about. It is surprising, then, that there is so little discussion of police unions, and the role that they play in shaping law enforcement practices and the policies that shape them.

The website for Black Lives Matter, admittedly a diffuse movement, does not mention police unions once in its“demands.” While labor unions’ support for Black Lives Matter is promoted on liberal websites, the role police unions play in these debates has not made its way into the national dialogue.

Recently, however, some activists associated with the movement included “fair police union contracts” in a ten-point set of policy solutions as part of a new effort called Campaign Zero. This is an important step that may signal a new phase of the broader movement.

Still, it is striking that police unions have escaped sustained, systemic critique from many of the most visible, mainstream politicians and pundits most eager to align with Black Lives Matter.

Why is this? Does the generally progressive ideological bent of some activists and supporters prevent them from a sustained critique against unions? Are politicians eager to say whatever the movement asks them — unless it costs them something like an endorsement by the Fraternal Order of Police?

Police officers deserve to be protected as they serve the community and their safety is imperative, but they should not be able to act with impunity. Police unions should understand that when they lash out at critics in defense of cops who misuse their authority, they weaken their ability to protect the good cops — the vast majority of police around the country.

The declaration of protesters that “black lives matter” has been right all along, of course.

The question for activists and politicians is whether they matter enough to take on one of the sacred cows of our politics. Police unions should be allies in efforts to reform our justice system, and we need to hold them accountable.

Michael Wearis a consultant and writer based in Washington D.C. He led faith outreach for the 2012 Obama campaign and worked as a White house aide.